JP5134472B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to an improvement in viewing angle characteristics of a liquid crystal display device.

Conventionally, in a liquid crystal display device, an optical film showing various optical characteristics is used for optical compensation in accordance with its mode. For example, as an optical compensation film for a TN mode liquid crystal display device, an optical compensation film having an optically anisotropic layer made of a liquid crystal composition on a transparent support made of a polymer film has been proposed (for example, Patent Document 1). .
In addition, instead of an optical compensation film having an optically anisotropic layer made of a liquid crystal composition, it has been proposed to use a polymer film whose optical axis is inclined in the thickness direction for optical compensation of a TN mode liquid crystal display device. (For example, patent document 2).

On the other hand, the liquid crystal display device is basically used not only as a display for a personal computer or the like used by one person but also as a display for a TV for a plurality of persons to observe from various directions. Therefore, further improvement in viewing angle characteristics is desired.
Japanese Patent No. 2587398 JP-A-7-333437

  An object of the present invention is to provide a liquid crystal display device with improved viewing angle characteristics.

Means for solving the above problems are as follows.
[1] A pair of polarizing layers arranged with their absorption axes orthogonal to each other;
Between the pair of polarizing layers, facing each other and at least one of which has a transparent electrode, the first substrate and the second substrate, and the first substrate and the second substrate. A liquid crystal cell having a liquid crystal layer formed thereon;
A liquid crystal having a first retardation layer between at least one of the pair of polarizing layers and the liquid crystal cell; and a second retardation layer between at least one of the pair of polarizing layers and the liquid crystal cell. A display device,
The first retardation layer has an asymmetry centered on the normal direction (polar angle 0 °) with respect to the incident light of at least one incident surface including the normal of the layer surface. A liquid crystal display device, wherein the second retardation layer is a layer containing molecules of a liquid crystal compound fixed in an alignment state.
[2] The liquid crystal display device according to [1], wherein the first retardation layer is made of a film in which a main axis of a refractive index ellipsoid is inclined in a thickness direction.
[3] The first retardation layer is made of a film satisfying an inclination angle θt of the principal axis of the refractive index ellipsoid with respect to the normal direction of the film surface satisfying 0 <θt ≦ 35 ° [1] The liquid crystal display device described.
[4] The in-plane retardation Re (550) of the first retardation layer at a wavelength of 550 nm is 0 nm <Re (550) ≦ 110 nm, and the retardation Rth (550) in the thickness direction at the same wavelength is 0 nm <Rth (550) ≦ 200 nm, the liquid crystal display device according to any one of [1] to [3].
[5] The first retardation layer is made of a film containing at least one selected from cyclic olefin copolymers, cellulose acylates, polyesters, and polycarbonates [1] Liquid crystal display device in any one of-[4].
[6] The first retardation layer is a film produced by passing a film-like melt of a composition containing a thermoplastic resin between two rolls having different peripheral speeds. The liquid crystal display device according to any one of [1] to [5].
[7] The liquid crystal display device according to any one of [1] to [6], wherein the first retardation layer is made of a stretched film.
[8] The [1] to [7], wherein the second retardation layer contains at least one of a discotic liquid crystal and a rod-like liquid crystal fixed in a hybrid alignment state in the film thickness direction. Any liquid crystal display device.
[9] The liquid crystal display device according to any one of [1] to [8], wherein the second retardation layer is a layer formed by polymerizing a composition containing a liquid crystalline monomer.
[10] The liquid crystal display device according to any one of [1] to [9], wherein the second retardation layer is disposed on the first retardation layer.
[11] The in-plane slow axis of the first retardation layer and the absorption axis of the polarizing layer positioned closer to the first retardation layer are parallel or orthogonal to each other [1] ] The liquid crystal display device according to any one of [10].
[12] The liquid crystal according to any one of [1] to [11], wherein Δn · d, which is a product of the thickness d of the liquid crystal layer and the birefringence index Δn, satisfies the following relational expression (I): Display device:
(I) 200 nm ≦ Δn · d ≦ 500 nm.
[13] In the state where no driving voltage is applied, liquid crystal molecules are aligned in parallel to the substrate surface in the liquid crystal layer, and the twist angle between the first and second substrates is 0] to [135 °. The liquid crystal display device according to any one of [1] to [12].

  According to the present invention, a liquid crystal display device with improved viewing angle characteristics can be provided.

  Hereinafter, the present invention will be described in more detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

In this specification, Re (λ) and Rth (λ) are in-plane retardation (nm) and retardation in the thickness direction (nm) at wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method. In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (if there is no slow axis, any in-plane film The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis of KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is changed to KOBRA 21ADH or WR after changing its sign to negative.
The retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis). Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following formulas (I) and (II).

式中、Ｒｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわす。
また、ｎｘは、面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表し、ｄは膜厚を表す。

In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
Nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, nz represents the refractive index in the direction perpendicular to nx and ny, and d Represents the film thickness.

When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotary axis), and −50 degrees to +50 degrees with respect to the film normal direction. Measured at 11 points by making light of wavelength λ nm incident from each tilted direction in 10 degree steps, and based on the measured retardation value, assumed value of average refractive index, and input film thickness value KOBRA 21ADH or WR is calculated.
In the above measurement, as the assumed value of the average refractive index, the values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical compensation films can be used.
Moreover, about the thing whose average refractive index value is not known, it can measure with an Abbe refractometer. Examples of the average refractive index values of main optical compensation films are as follows:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
The Re, Rth, and refractive index measurement wavelengths are values at λ = 550 nm in the visible light region unless otherwise specified.
In the present specification, the “principal axis” means the principal refractive index in the film thickness direction unless otherwise specified in the principal refractive index axis of the refractive index ellipsoid calculated by KOBRA 21ADH or WR, nx, ny, nz. It means rate nz.

FIG. 1 is a schematic diagram conceptually showing the structure of an example of the liquid crystal display device of the present invention.
The liquid crystal display device of FIG. 1 includes a pair of polarizing layers 18 and 20 that are disposed so that their absorption axes are orthogonal to each other, and a first substrate 14 and a pair that are disposed to face each other between the pair of polarizing layers 18 and 20. Between the liquid crystal cell LC having the second substrate 16 and the liquid crystal layer 12 disposed between the first substrate 14 and the second substrate 16, between each of the polarizing layers 18 and 20 and the liquid crystal cell LC The second retardation layers 26 and 28 are provided between the first retardation layers 22 and 24 and the polarizing layers 18 and 20 and the liquid crystal cell LC, respectively.

  The liquid crystal cell LC is a TN mode liquid crystal cell, and an electrode layer is formed on the opposing surfaces of the first and second substrates 14 and 16. An example is provided with a plurality of TFTs respectively corresponding to a plurality of pixel electrodes, a plurality of gate wirings for supplying gate signals to the TFTs in each row, and a plurality of data wirings for supplying data signals to the TFTs in each column, Each of the plurality of pixel electrodes is connected to a TFT corresponding to the pixel electrode. Further, on the opposing surfaces of the pair of opposing substrates 14 and 16, horizontal alignment films that are aligned in directions 14 a and 16 a substantially orthogonal to each other are formed so as to cover the electrode layers. The liquid crystal layer 12 is a layer formed by filling a nematic liquid crystal material having positive dielectric anisotropy, and the liquid crystal molecules are aligned in the vicinity of the first and second substrates 14 and 16 by a horizontal alignment film. When an electric field is not applied between the electrode layers, the substrate is twisted with a twist angle of about 90 ° between the substrates 14 and 16, as shown in FIG. On the other hand, when a voltage for black display is applied between the electrodes, the liquid crystal molecules rise perpendicular to the surfaces of the substrates 14 and 16. In this state, the polarization state of the light propagating in the liquid crystal layer differs depending on the orientation of the liquid crystal molecules between the case where light is incident on the liquid crystal layer from the normal direction and the case where light is incident from an oblique direction. As a result, the contrast is lowered depending on the viewing angle, and gradation inversion and color shift occur. In the liquid crystal display device 10 of FIG. 1, the combination of the first retardation layers 22 and 24 and the second retardation layers 26 and 28 reduces the viewing angle dependency of display characteristics such as contrast, and the viewing angle. The characteristics are improved.

Δn · d, which is the product of the thickness d of the liquid crystal layer 12 and the birefringence index Δn, is generally about 300 to 500 nm in the TN mode and about 250 to 350 nm in the ECB mode. In the present invention, it is preferable that Δn · d of the liquid crystal layer satisfies the following formula because a viewing angle expansion effect is obtained in each of the TN and ECB modes.
(I) 200 nm ≦ Δn · d ≦ 500 nm.
Δn · d is more preferably 380 to 450 nm in the TN mode and 280 to 320 nm in the ECB mode.

The liquid crystal layer 12 is preferably a multi-gap liquid crystal layer having different thicknesses between the RGB sub-pixel regions. For example, the thickness of the color filter is not uniform, and the thickness of the R subpixel, the G subpixel, and the B subpixel can be changed to form a multi-gap liquid crystal layer. As an example, Δnd (R) of the liquid crystal layer corresponding to the R subpixel, Δnd (G) of the liquid crystal layer corresponding to the G subpixel, and Δnd (B) of the liquid crystal layer corresponding to the B subpixel are Δnd (B ) <Δnd (G) <Δnd (R). According to this example, a color image with high contrast and color reproducibility can be displayed over a wide viewing angle.
On the other hand, as a liquid crystal material, Δn has wavelength dependency, and Δn (R) for R light, Δn (G) for G light, and Δn (B) for B light are Δn (B) <Δn (G) <Δn. By using a liquid crystal material satisfying the relationship (R), the same effect can be obtained even if the thickness of the color filter is uniform.

  The liquid crystal display device shown in FIG. 1 is a normally white mode, and has a pair of polarizing layers 18 and 20 (hereinafter, the upper polarizing layer 18 is the first polarizing layer 18 and the lower polarizing layer 20 is the second polarizing layer). 1), the respective absorption axes 18a and 20a are arranged substantially orthogonal to each other, as shown in FIG.

  Between the liquid crystal cell LC and the pair of polarizing layers 18 and 20, first retardation layers 22 and 24 and second retardation layers 26 and 28 are disposed, respectively. In the first retardation layers 22 and 24, the polar angle dependence of retardation is asymmetric with respect to the normal direction (polar angle 0 °) with respect to incident light on at least one incident surface including the normal of the layer surface. On the other hand, the second retardation layer contains molecules of a liquid crystal compound fixed in an aligned state. The first retardation layer is used as a support for the second retardation layer, and a second retardation layer made of a liquid crystal composition is formed thereon, and optical compensation films F1 and F2 are produced. It can be incorporated in a liquid crystal display device. Furthermore, in the aspect in which the first retardation layers 22 and 24 are polymer films, they can be bonded to the polarizing layers 18 and 20 and used as a protective film. In the said aspect, the polarizing plates PL1 and PL2 in FIG. 1 can be manufactured, it can be bonded to liquid crystal cell LC, and a liquid crystal display device can be manufactured.

  In the first retardation layers 22 and 24, the polar angle dependence of retardation is asymmetric with respect to the normal direction (polar angle 0 °) with respect to incident light on at least one incident surface including the normal of the layer surface. Have sex. Specifically, at a wavelength of 550 nm, in a plane (incident surface) including a normal line orthogonal to the in-plane slow axis of the first retardation layer, from a direction inclined by 40 ° from the normal line to the film surface direction. The ratio of the measured retardation R [+ 40 °] to the retardation R [−40 °] measured from the direction inclined 40 ° from the normal line is 1 <R [+ 40 °] / R [−40 °]. Satisfied. More preferably, 1 <R [+ 40 °] / R [−40 °] ≦ 100. However, the direction of + 40 ° and the opposite direction of −40 ° is determined so that R [+ 40 °]> R [−40 °]. FIG. 3 is a schematic diagram illustrating an example of the relationship between the in-plane slow axis, the incident surface, and the incident direction of the retardation layer when measuring R [+ 40 °] and R [−40 °]. The measurement of R [+ 40 °] and R [−40 °] may be in any of the incident directions 1 and 2, and is determined so as to satisfy the relationship of R [+ 40 °]> R [−40 °]. . Hereinafter, the same applies to the second retardation layer and the optical compensation film. An example of the first retardation layer that satisfies such characteristics is that its principal axis is in the direction of an inclination angle θt (provided that 0 ° <θt <90 ° is satisfied) with respect to the normal direction of the layer surface, that is, A film in which the main axis is inclined in the thickness direction of the layer. The inclination angle θt is determined so as to satisfy the optical characteristics required for optical compensation as a whole in consideration of the optical characteristics and the like of the second retardation layer. The inclination angle θt preferably satisfies 0 ° <θt ≦ 35 °, and more preferably satisfies 0 <θt ≦ 20 °.

  A polymer film satisfying the above-described characteristics that can be used for the first retardation layer is obtained by melt-extruding a positive intrinsic birefringent amorphous thermoplastic resin into a film shape, and then between rolls having different peripheral speeds. It can manufacture by letting pass. A method for producing a polymer film usable for the first retardation layer will be described later.

  The second retardation layers 26 and 28 are layers formed by bringing the curable liquid crystal composition into a desired alignment state and then curing it. For example, it can be produced by applying a polymerizable liquid crystal to the alignment treatment surface of the alignment film, aligning it along the alignment treatment direction (generally a rubbing axis), and fixing the alignment state. As an example, there is a retardation layer formed by fixing discotic liquid crystal molecules in a so-called hybrid alignment state. In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the layer surface increases or decreases in the depth direction of the layer and with an increase in the distance from the alignment film surface. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the angle does not change in the middle of the thickness direction. In the present specification, “hybrid orientation” includes an orientation state in which the angle does not change, or the orientation state increases or decreases as a whole. Hybrid orientation in which the angle continuously changes is preferable. Materials and the like that can be used for producing the retardation layer will be described later.

  A retardation layer in which a disk-like liquid crystal composition is hybrid-aligned and its alignment state is fixed is also normal to the polar angle dependence of retardation with respect to incident light on at least one incident surface including the normal of the layer surface. It has asymmetry around the direction (polar angle 0 °). Specifically, at a wavelength of 550 nm, measurement was performed from a direction inclined by 40 ° from the normal to the film surface direction in an in-plane (incident surface) including a normal perpendicular to the in-plane slow axis of the retardation layer. Ratio of retardation R [+ 40 °] and retardation R [−40 °] measured from a direction inclined by 40 ° from the normal line satisfies 1 <R [+ 40 °] / R [−40 °] To do. More preferably, 3 ≦ R [+ 40 °] / R [−40 °] ≦ 15 (provided that the direction of + 40 ° and vice versa is R [+ 40 °]> R [−40 °]. To be determined).

The optical compensation films F1 and F2 as a whole
(1) In-plane retardation Re (550) at a wavelength of 550 nm is 0 nm <Re (550) ≦ 230 nm (more preferably 0 nm <Re (550) ≦ 100 nm);
(2) Letter measured from a direction inclined by 40 ° from the normal to the film surface direction in a plane (incident surface) including a normal perpendicular to the in-plane slow axis of the entire optical compensation film at a wavelength of 550 nm Retardation R [+ 40 °] or retardation R [-40 °] measured from a direction inclined -40 ° from the normal to the film surface direction is 0 nm to 300 nm (more preferably 0 to 150 nm); and ( 3) Retardation measured at a wavelength of 550 nm from a direction inclined by 40 ° from the normal to the film plane in an in-plane (incident plane) including a normal perpendicular to the in-plane slow axis of the optical compensation film as a whole. The ratio of R [+ 40 °] and retardation R [−40 °] measured from a direction inclined by 40 ° from the normal is 1 <R [+ 40 °] / R [−40 °. (More preferably 1 <R [+ 40 °] / R [-40 °] ≦ 100) satisfies.
When the optical compensation film comprising the combination of the first and second retardation layers satisfies the above conditions (1) to (3), the TN mode liquid crystal cell can be optically compensated more accurately, and the viewing angle The characteristics are further improved.

Next, the optical axis relationship of the liquid crystal display device shown in FIG. 1 will be described.
In the liquid crystal display device shown in FIG. 1, the alignment processing direction (usually the rubbing axis) 14a of the alignment film formed on the opposing surface of the first substrate 14 is on the display surface side with respect to the horizontal direction of the screen of the liquid crystal display device. The alignment processing direction 16a of the alignment film formed on the opposing surface of the second substrate 16 is 45 ° counterclockwise as viewed from the upper side of the drawing. When viewed from the observer side (upper side of the drawing), the rotation is clockwise 45 °. When no voltage is applied, the liquid crystal molecules in the vicinity of the alignment film interface are aligned so that the major axis direction coincides with the alignment processing direction, so that the twist alignment is substantially 90 ° clockwise when viewed from the display surface side. doing.

  The first polarizing layer 18 is arranged with its absorption axis 18a parallel to the alignment treatment direction 14a of the alignment film, and the second polarizing layer 20 has its absorption axis 20a as the first polarizer layer. The 18 absorption axes 18a are arranged so as to be substantially orthogonal. That is, the absorption shaft 18a is in a direction rotated 45 ° counterclockwise as viewed from the display surface side, and the absorption shaft 20a is in a direction rotated clockwise 45 ° as viewed from the display surface side and orthogonal to each other. Yes. The absorption shaft 18a is in a direction rotated 45 ° clockwise as viewed from the display surface side, and the absorption shaft 20a is in a direction rotated 45 ° counterclockwise as viewed from the display surface side and are orthogonal to each other. However, the same display characteristics are obtained.

  In FIG. 1, the in-plane slow axis 22a of the first retardation layer 22 and the in-plane slow axis 26a of the second retardation layer 26 of the optical compensation film F1 on the display surface side, and the first substrate 14 The alignment processing direction 14a of the alignment film is substantially orthogonal, and the in-plane slow axis 24a of the first retardation layer 24 and the surface of the second retardation layer 28 of the optical compensation film F2 on the backlight side. The inner slow axis 28a and the alignment treatment direction 16a of the alignment film of the second substrate 16 are substantially orthogonal. In FIG. 1, in the optical compensation film F1, the slow axis 22a of the first retardation layer 22 and the slow axis 26a of the second retardation layer 26 are parallel to each other. The slow axis 24a of the retardation layer 24 and the slow axis 28a of the second retardation layer 28 are parallel to each other. In this configuration example, in order to widen the viewing angle of the TN mode liquid crystal display device, Re (550) of the optical compensation films F1 and F2 as a whole is 0 nm <Re (550) ≦ 230 nm, and at a wavelength of 550 nm, Retardation R [+ 40 °] measured from a direction inclined by 40 ° from the normal to the film surface direction in an in-plane (incident surface) including a normal perpendicular to the in-plane slow axis of the optical compensation film as a whole, or It is preferable that the retardation R [−40 °] measured from a direction inclined by −40 ° from the normal to the film surface direction is 0 nm to 300 nm. In addition, the inclination angle θt of the main axes of the first retardation layers 22 and 24 is preferably 0 <θt ≦ 35 °.

  Further, the direction in which the retardation in the tilt direction of the principal axis of the first retardation layer 22 (or 24) is tilted from the normal direction is decreased, and the direction of the alignment treatment of the substrate 14 (or substrate 16) ( Usually, the rubbing direction) 14a (or 16a) is preferably arranged substantially in parallel. Arranging in this relationship is preferable because the viewing angle is enlarged.

FIG. 2 is a conceptual diagram schematically showing another configuration example of the liquid crystal display device of the present invention. In FIG. 2, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
In the liquid crystal display device shown in FIG. 2, the in-plane slow axis 22a ′ of each of the first retardation layer 22 ′ in the optical compensation film F1 ′ and the second retardation layer 24 ′ in the optical compensation film F2 ′. And 24a ′ are offset from the liquid crystal display device of FIG. 1 by 90 °. That is, in the optical compensation film F1 ′, the in-plane slow axis 22a ′ of the first retardation layer 22 ′ and the in-plane slow axis 26a of the second retardation layer 26 are orthogonal, and the optical compensation film F2 ′. Among these, the in-plane slow axis 24 a ′ of the first retardation layer 24 ′ and the in-plane slow axis 28 a of the second retardation layer 28 are orthogonal to each other. Also in this configuration example, the TN mode liquid crystal display device can have a wide viewing angle as in FIG. In a preferred embodiment, Re (550) of the optical compensation films F1 ′ and F2 ′ as a whole is 0 nm <Re (550) ≦ 100 nm, and is orthogonal to the in-plane slow axis of the whole optical compensation film at a wavelength of 550 nm. In the plane including the normal line (incident surface), the retardation R [+ 40 °] measured from the direction inclined by 40 ° from the normal line to the film surface direction or −40 ° inclined from the normal line to the film surface direction The retardation R [−40 °] measured from the direction is preferably 0 nm to 300 nm. In addition, the inclination angle θt of the main axes of the first retardation layers 22 and 24 is preferably 0 <θt ≦ 35 °.

  A film satisfying the optical characteristics required for the first retardation layer can be produced by passing a film-like melt between two rolls having different peripheral speeds. In that case, the main axis | shaft of a film inclines in the conveyance direction (henceforth "MD direction") of a film. In continuous production, the film-like melt is passed between two rolls with different peripheral speeds, subjected to stretching treatment as desired, and then a liquid crystal composition is applied to form a second retardation layer. To do. The projection axis obtained by projecting the principal axis of the polymer film produced by this method onto the layer surface is parallel to the MD direction and orthogonal to the in-plane slow axis. On the other hand, when the second retardation layer is a layer formed by fixing liquid crystal molecules in a hybrid alignment state on the rubbing surface, the in-plane slow axis is generally perpendicular to the rubbing direction. It is. In the method of continuously forming such a layer on the film, a rubbing treatment is performed in parallel with the MD direction while a long film is conveyed, a liquid crystal composition is applied to the treated surface, and the layer is formed. It is common to form. Therefore, the in-plane slow axis of the layer is a direction orthogonal to the MD direction. In the optical compensation film F1 (or F2) in FIG. 1, the in-plane slow axis 22a (or 24a) of the first retardation layer 22 (or 24) and the second retardation layer 26 (or 28) This is a configuration example in which the in-plane slow axis 26a (or 28a) is in the parallel direction and can be manufactured by the continuous manufacturing method. On the other hand, in the optical compensation film F1 ′ (or F2 ′) of FIG. 2, the in-plane slow axis 22′a (or 24′a) of the first retardation layer 22 ′ (or 24 ′) and the second The in-plane slow axis 26'a (or 28'a) of the retardation layer 26 '(or 28') is in the orthogonal direction and cannot be produced by the above continuous production method. For example, the second retardation layer When forming, it is necessary to perform a rubbing process in a direction orthogonal to the transport direction. Therefore, in the aspect in which the second retardation layer is produced using the hybrid alignment of the disc-like liquid crystal, the example of FIG. 1 can be continuously produced more stably than the example of FIG. Excellent in terms.

  Although the aspect of the liquid crystal display device in the TN (Twisted Nematic) mode has been described above, the liquid crystal display device is not limited to the TN mode, and the liquid crystal display device in the same manner as the OCB (Optically Compensatory Bend) and ECB (Electrically Controlled Birefringence) modes. effective.

  In one embodiment of the ECB mode liquid crystal display device, Δn · d of the liquid crystal layer in the liquid crystal cell is about 250 to 350 nm, and the directions of the alignment treatment applied to the inner surfaces of the pair of cell substrates are parallel to each other and do not intersect. That is, the liquid crystal in the liquid crystal cell is not twisted when no electric field is applied. The pair of polarizing layers are arranged with their absorption axes orthogonal to each other, and the respective absorption axes are set to 45 ° with respect to the alignment treatment direction applied to the inner surface of the cell substrate arranged at a closer position. Arranged. The relationship between the in-plane slow axis of the first retardation layer and the absorption axis of the polarizing layer disposed at a closer position is the same as in the TN mode.

Hereafter, each member utilized for the liquid crystal display device of this invention is demonstrated.
First retardation layer:
In the present invention, the polar phase dependence of retardation is centered on the normal direction (polar angle 0 °) with respect to incident light on at least one incident surface including the normal of the layer surface of the first retardation layer. The first retardation layer having asymmetry is used. An example of the first retardation layer is a film in which the main axis of the refractive index ellipsoid is inclined in the thickness direction. “Inclined in the thickness direction” means an angle θt (where 0 ° <θt <90 °) in the film surface direction, with an arbitrary direction in the film surface as an inclination direction with respect to the normal direction of the film surface. In the following, it means that θt is inclined by “inclination angle”). The first retardation layer is made of a film having a main axis in a direction of an inclination angle θt (more preferably 0 <θt ≦ 20 °) satisfying 0 <θt ≦ 35 ° with respect to the normal direction of the film surface. Is preferred.

In addition, the inclination angle with respect to the film surface of the main axis of the film can be measured by the following method. Note that an error that is allowed in the following measurement method will also be allowed for the tilt angle θt of the main axis of the film used in the present invention.
The tilt angle θt of the main axis of the film is measured using the KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) with the width direction (TD direction) of the film as the tilt axis, and the phase difference at a tilt angle of 40 degrees. And the inclination angle of the main axis is measured from the phase difference at an inclination angle of −40 degrees. The measurement wavelength is 550 nm.
Further, the variation in the inclination angle of the main shaft can be measured by the following method.
Sampling is performed at 10 points in the width direction of the film and 10 points in the transport direction at equal intervals, and the tilt angle of the main shaft is measured by the above method, and the difference between the maximum value and the minimum value is defined as the variation in the tilt angle of the main shaft. be able to.
The slow axis angle can be determined by the above-described measurement of Re, and the variation is also the maximum value when measurement is performed at equal intervals of 10 points in the width direction of the film and 10 points in the transport direction. It can be determined by the difference between the minimum values.

  The preferred ranges of Re and Rth of the first retardation layer vary depending on the optical characteristics of the second retardation layer, but Re (550) is 0 nm <Re (550) ≦ 110 nm, and Rth ( 550) is preferably from 0 to 200 nm.

The first retardation layer of the above aspect can be produced, for example, by the following method.
The film-like melt of the composition containing the thermoplastic resin can be produced by a method including passing between two rolls having different peripheral speeds and further stretching as required. By this method, a polymer film that satisfies the optical characteristics as the first retardation layer can be stably and easily produced.
Hereinafter, this manufacturing method will be described in detail.

In the method, a composition containing a thermoplastic resin (sometimes referred to as a “thermoplastic resin composition”) is melt-extruded. Prior to melt extrusion, the thermoplastic resin composition is preferably pelletized. Pelletization can be made by drying the thermoplastic resin composition, melting it at 150 ° C. to 300 ° C. using a twin-screw kneading extruder, and then solidifying and cutting the extruded noodle in air or water. . Further, after melting by an extruder, it can be pelletized by an underwater cutting method in which it is cut while being directly extruded from a die into water. Extruders used for pelletization include single screw extruders, non-meshing different direction rotating twin screw extruders, meshing different direction rotating twin screw extruders, and meshing same direction rotating twin screw extruders. Etc. can be used. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes.
No particular limitation is imposed on the size of the pellets is generally about 10mm ³ ~1000mm ^3, more preferably about 30 mm ³ 500 mm ^3.

  It is preferred to reduce the moisture in the pellets prior to melt extrusion. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C. Thereby, the moisture content is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

  Next, the dried pellets are supplied into the cylinder through the supply port of the extruder, and are kneaded and melted. The inside of the cylinder is composed of, for example, a supply unit, a compression unit, and a measurement unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5, the ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. The extrusion temperature is determined according to the melting temperature of the thermoplastic resin, but generally about 190 to 300 ° C is preferable. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using an extruder with a vent.

  It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign matter in the thermoplastic resin composition. Filtration may be performed in one stage or may be performed in multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

  In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. Thereby, the resin pressure fluctuation width in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the die to increase the uniformity of the resin temperature. The clearance of the T-die exit portion is generally 1.0 to 10 times the film thickness, preferably 1.2 to 5 times.
The die is preferably adjustable in thickness at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to die thickness adjustment is also effective.
In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.
Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 to 40 minutes, more preferably 4 to 30 minutes.

Next, the melt of the thermoplastic resin is extruded from the die into a film, passed between two rolls (for example, a touch roll and a casting roll), and cooled and solidified (touch roll method) to obtain a film. In the method, the film-like melt is passed between two rolls rotating at different peripheral speeds, so that the film is sheared and incident light on at least one incident surface including the normal of the layer surface On the other hand, a polymer film is produced in which the polar angle dependency of retardation has asymmetry centering on the normal direction (polar angle 0 °). When a roll having a large diameter is used, the shear applied to the film increases, and the inclination angle of the main shaft tends to increase. It is preferable to use two rolls (for example, a touching roll and a casting roll) having a diameter of 350 to 600 nm (more preferably 350 to 500 nm). When a roll with a large diameter is used, the contact area between the film-like melt and the roll becomes wider, and the time for shearing becomes longer, so that the film with the main axis inclined at a larger inclination angle is suppressed and the variation is suppressed. Can be manufactured. In the method of the present invention, the diameters of the two rolls may be the same or different. Moreover, since the biting property of the film is improved, the film can be manufactured more stably. On the other hand, if the temperature distribution in the width direction of the film-like melt is remarkable, it becomes difficult to maintain uniformity. Therefore, in the above method, immediately before being melt-extruded from the die and contacting at least one of the two rolls. Until then, it is preferable to reduce the temperature distribution in the width direction of the melt, and specifically, the temperature distribution in the width direction is preferably within 5 ° C. In order to reduce the temperature distribution, a member having a heat insulating function or a heat reflecting function is arranged in at least a part of the passage between the melt die and the two rolls to shield the melt from the outside air. Is preferred. Thus, by arranging the heat insulating member in the passage and shielding it from the outside air, it is possible to suppress the influence of the external environment, for example, wind, and to suppress the temperature distribution in the width direction of the film. The temperature distribution in the width direction of the film-like melt is more preferably within ± 3 ° C, and still more preferably within ± 1 ° C. Thus, the variation which makes uniform the temperature of the width direction of a film-form melt can be suppressed until just before passing between rolls.
The temperature distribution of the film-like melt can be measured with a contact-type thermometer or a non-contact type thermometer, and in particular, can be measured with a non-contact-type infrared thermometer.

  As a method of eliminating the variation, there is a method of increasing the adhesion when the film-like melt comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be performed on the entire surface of the film-like melt or may be partially performed.

In the present invention, the material of the two rolls is preferably a metal, more preferably stainless steel, and a roll whose surface is plated is also preferred. On the other hand, it is preferable not to use a rubber roll or a metal roll lined with rubber because the surface has large irregularities and the film surface is easily damaged.
As for the touch roll, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP2003. -145609 can be used.

  In addition to two rolls (for example, a casting roll and a touch roll) that allow the film-like melt to pass through, it is preferable to use one or more casting rolls to cool the film. The touch roll is usually arranged so as to touch the first casting roll on the most upstream side (closer to the die). In general, it is relatively common to use three cooling rolls, but this is not a limitation. The distance between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still more preferably 3 mm to 30 mm between the surfaces.

  The surface of the touch roll or casting roll has an arithmetic average height Ra of usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less.

Here, the peripheral speed ratio of the two rolls means the ratio of the peripheral speeds of the two rolls (the peripheral speed of the first roll / the peripheral speed of the second roll). However, the peripheral speed of the first roll <the peripheral speed of the second roll. The larger the peripheral speed difference between the two rolls, that is, the smaller the above-mentioned peripheral speed ratio, the greater the inclination angle of the main axis of the film obtained. On the other hand, if the peripheral speed difference is too large, the resulting film It becomes easy to be damaged on the surface. Specifically, when producing a polymer film having a large inclination angle θt of the main shaft, for example, 20 ° or more, the peripheral speed ratio of the two rolls is preferably 0.55 to 0.80, and 0 It is more preferable to set it as 55-0.74. However, it is preferable to satisfy the following conditions (i) to (iii) so as not to be scratched.
(I) Temperature range where the viscoelasticity of the melt of the thermoplastic resin composition immediately before contacting at least one of the two rolls shows loss elastic modulus> storage elastic modulus (specifically, Tg + 50 ° C. to Tg + 70 ° C. or more ( Tg is the glass transition point of the thermoplastic resin)),
(Ii) The temperature distribution in the width direction of the melt is within ± 5 ° C. until just before the film-like melt melt-extruded from the die comes into contact with at least one of the two rolls.
(Iii) As the two rolls, use is made of a roll having a metal surface at least.

  The two rolls may be driven or driven independently, but in order to control the variation in the optical axis, it is preferable that the two rolls be driven independently. In the present invention, the two rolls are driven at different peripheral speeds as described above. However, the surface temperatures of the two rolls may be further differentiated. A preferable temperature difference is 5 ° C to 80 ° C, more preferably 20 ° C to 80 ° C, and further preferably 20 ° C to 60 ° C. In that case, the temperature of two rolls becomes like this. Preferably it sets to 60 to 160 degreeC, More preferably, it is 70 to 150 degreeC, More preferably, it sets to 80 to 140 degreeC. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.

It is preferable to trim both ends after the melt is formed into a film. The portion cut off by trimming may be crushed and used again as a raw material.
Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C. It is also preferable to attach a lami film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.
The winding tension is preferably 2 kg / m width to 50 kg / width, more preferably 5 kg / m width to 30 kg / width.

In order to produce a polymer film that satisfies the characteristics required for the first retardation layer, the film may be stretched and / or relaxed. For example, each step can be performed by the following combinations (a) to (i).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) longitudinal stretching → lateral stretching (d) longitudinal stretching → lateral stretching → relaxation treatment (e) longitudinal stretching → relaxation treatment → lateral stretching → relaxation treatment (f) Stretching → Longitudinal stretching → Relaxation treatment (g) Transverse stretching → Relaxation treatment → Longitudinal stretching → Relaxation treatment (h) Longitudinal stretching → Transverse stretching → Longitudinal stretching (i) Longitudinal stretching → Transverse stretching → Longitudinal stretching → Relaxation treatment Among these What is particularly required is the transverse stretching step (a).

  The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg to Tg + 30 ° C or less. Moreover, a preferable lateral stretch ratio is 1.01 to 4 times, more preferably 1.03 to 3.5 times, and still more preferably 1.05 to 3.0 times. The transverse draw ratio is particularly preferably 1.5 to 3.0 times.

By performing preheating before stretching and heat setting after stretching, the Re and Rth distribution after stretching can be reduced, and the variation in orientation angle associated with bowing can be reduced. Either preheating or heat setting may be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding with a clip, that is, preferably performed continuously with stretching.
Preheating can be performed at a temperature about 1 ° C. to 50 ° C. higher than the stretching temperature, preferably 2 ° C. to 40 ° C. or less, more preferably 3 ° C. or more and 30 ° C. or less. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.
The heat setting can be performed at a temperature 1 ° C. or more and 50 ° C. or less lower than the stretching temperature, more preferably 2 ° C. or more and 40 ° C. or less, and further preferably 3 ° C. or more and 30 ° C. or less. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain is likely to occur in the film, and it is not preferable because it is likely to increase the variation with time of Re and Rth.

  The reason why the variation in orientation angle and Re and Rth can be reduced by such preheating and heat setting is as follows. (I) The film is stretched in the width direction and tends to become thin in the orthogonal direction (longitudinal direction) (necking phenomenon). For this reason, the film before and after transverse stretching is pulled and stress is generated. However, both ends in the width direction are fixed by a chuck and are not easily deformed by stress, and the central portion in the width direction is easily deformed. As a result, the stress due to necking is deformed into a bow shape and bowing occurs. As a result, in-plane Re and Rth unevenness and distribution of orientation axes occur. (ii) To suppress this, if the temperature on the preheating side (before stretching) is increased and the temperature on the heat treatment (after stretching) is decreased, neck-in occurs on the high temperature side (preheating) with a lower elastic modulus, It is difficult to generate by heat treatment (after stretching). As a result, bowing after stretching can be suppressed.

By such stretching, variations in the width direction and the longitudinal direction of Re and Rth can both be 5% or less, more preferably 4% or less, and even more preferably 3% or less. Further, the orientation angle can be 90 ° ± 5 ° or less or 0 ° ± 5 ° or less, more preferably 90 ° ± 3 ° or less, or 0 ° ± 3 ° or less, and further preferably 90 ° ± 1 ° or less or It can be 0 ° ± 1 ° or less.
A high-speed stretching process may be performed, and the stretching process can be performed preferably at 20 m / min or more, more preferably 25 m / min or more, and further preferably 30 m / min or more.

  The film that can be used as the first retardation layer contains a thermoplastic resin exhibiting positive intrinsic birefringence. The thermoplastic resin is preferably amorphous. The intrinsic birefringence of various resins is described in MSDS, resin specification table, polymer database, etc., and can be referred to. Moreover, when it is not described in any book etc., it can measure according to the prism coupling method. In the present invention, “amorphous resin” refers to a resin having no crystal melting peak when a thermal analysis measurement is performed on a film on which the resin is formed. As long as the above properties are satisfied, the type of resin is not particularly limited. Examples of thermoplastic resins include cyclic olefin copolymers, cellulose acylates, polyesters, and polycarbonates. In the case of producing using a melt extrusion method, it is preferable to use a material having good melt extrusion moldability. From this viewpoint, it is preferable to select cyclic olefin copolymers and cellulose acylates. One kind of the resin may be contained, or two or more kinds of the resins different from each other may be contained. Of these, cellulose acylates and cyclic olefin resins obtained by addition polymerization are preferred.

Examples of the cyclic olefin copolymers include a resin obtained by polymerization of a norbornene compound. It may be a resin obtained by any polymerization method of ring-opening polymerization and addition polymerization.
Examples of the addition polymerization and the resin obtained thereby include, for example, Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3871721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, and Japanese Translation of PCT International Publication No. 2005-527696. JP-A-2006-28993, JP-A-2006-11361, International Publication WO 2006/004376, International Publication WO 2006/0307077, and the like. Among these, those described in Japanese Patent No. 3517471 are particularly preferable.
Examples of the ring-opening polymerization and the resin obtained thereby include WO 98/144499, pamphlet, patent 30605532, patent 3220478, patent 373046, patent 334027, patent 3428176, patent. Examples are described in Japanese Patent No. 3687231, Japanese Patent No. 3873934, and Japanese Patent No. 3912159. Of these, those described in International Publication WO 98- / 14499 pamphlet and Japanese Patent No. 30605532 are particularly preferable.
Of these cyclic olefins, addition polymerization is more preferable. A commercially available product may be used, and in particular, “TOPAS # 6013” (manufactured by Polyplastics Co., Ltd.) that can easily suppress gel generated during extrusion molding can be used.

  Examples of the cellulose acylates include any cellulose acylate in which at least a part of three hydroxyl groups in the cellulose unit is substituted with an acyl group. The acyl group (preferably an acyl group having 3 to 22 carbon atoms) may be either an aliphatic acyl group or an aromatic acyl group. Among them, cellulose acylate having an aliphatic acyl group is preferable, those having an aliphatic acyl group having 3 to 7 carbon atoms are more preferable, those having an aliphatic acyl group having 3 to 6 carbon atoms are more preferable, and carbon number More preferably has 3 to 5 aliphatic acyl groups. A plurality of these acyl groups may be present in one molecule. Examples of preferred acyl groups include acetyl, propionyl, butyryl, pentanoyl, hexanoyl and the like. Among these, cellulose acylate having one or more selected from acetyl group, propionyl group and butyryl group is more preferable, and more preferable one has both acetyl group and propionyl group. Cellulose acylate (CAP). CAP is preferable in terms of easy resin synthesis and high stability of extrusion molding.

When producing a film by the melt extrusion method, it is preferable that the cellulose acylate to be used satisfies the following formulas (S-1) and (S-2). Cellulose acylate satisfying the following formula has a low melting temperature and improved meltability, and is therefore excellent in melt extrusion film formation.
Formula (S-1) 2.5 ≦ X + Y ≦ 3.0
Formula (S-2) 1.25 ≦ Y ≦ 3.0
In the formula, X represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the sum of the degree of substitution of the acyl group with respect to the hydroxyl group of cellulose. The “degree of substitution” in the present specification means the total of the ratio of substitution of hydrogen atoms of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the degree of substitution is 3.
Furthermore, it is more preferable to use a cellulose acylate that satisfies the following formula:
2.6 ≦ X + Y ≦ 2.95
2.0 ≦ Y ≦ 2.95
It is more preferable to use a cellulose acylate that satisfies the following formula.
2.7 ≦ X + Y ≦ 2.95
2.3 ≦ Y ≦ 2.9

  There is no restriction | limiting in particular about the mass average polymerization degree and number average molecular weight of cellulose acylates. In general, the mass average degree of polymerization is about 350 to 800, and the number average molecular weight is about 70000 to 230,000. The cellulose acylates can be synthesized using acid anhydrides or acid chlorides as acylating agents. In the industrially most general synthesis method, cellulose obtained from cotton linter, wood pulp, etc. is converted into organic acids (acetic acid, propionic acid, butyric acid) corresponding to acetyl groups and other acyl groups, or their acid anhydrides (anhydrous anhydride). A cellulose ester is synthesized by esterification with a mixed organic acid component containing acetic acid, propionic anhydride, and butyric anhydride). As a method for synthesizing cellulose acylate satisfying the above formulas (S-1) and (S-2), the Technical Report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) 7 Pp. 12 to 12, JP-A-2006-45500, JP-A-2006-241433, JP-A-2007-138141, JP-A-2001-188128, JP-A-2006-142800, JP-A-2007. Reference can be made to the method described in Japanese Patent No. 98917.

  Examples of the polyester include a polyester resin which is a diol unit having a cyclic acetal skeleton, and in particular, a diol unit containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit has a cyclic acetal skeleton. A polyester resin having a small birefringence is preferably used in the present invention.

  The polymer film used for the first retardation layer may contain a material other than the thermoplastic resin, but contains one or more of the thermoplastic resins as a main component (all the components in the composition). It means a material with the highest content ratio in the material, and in an embodiment containing two or more of the resins, it means that the total content ratio thereof is higher than the respective content ratios of other materials) It is preferable. Examples of materials other than the thermoplastic resin include various additives, and examples thereof include a stabilizer, an ultraviolet absorber, a light stabilizer, a plasticizer, fine particles, and an optical adjusting agent.

Stabilizer:
The optical film of the present invention may contain at least one stabilizer. The stabilizer is preferably added before or when the thermoplastic resin is heated and melted. The stabilizer has effects such as preventing oxidation of the film constituting material, capturing an acid generated by decomposition, and suppressing or inhibiting a decomposition reaction caused by radical species caused by light or heat. Stabilizers are useful for suppressing the occurrence of alterations such as coloring and molecular weight reduction and the generation of volatile components due to various decomposition reactions including unresolved decomposition reactions. Even at the melting temperature for forming a resin film, the stabilizer itself is required to function without being decomposed. Typical examples of stabilizers include phenol-based stabilizers, phosphorous acid-based stabilizers (phosphite-based), thioether-based stabilizers, amine-based stabilizers, epoxy-based stabilizers, and lactone-based stabilizers. Stabilizers, amine stabilizers, metal deactivators (tin stabilizers) and the like are included. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Then, it is preferable to use at least one or more of a phenol-based or phosphorous acid-based stabilizer. Among phenolic stabilizers, it is particularly preferable to add a phenolic stabilizer having a molecular weight of 500 or more. Preferable phenolic stabilizers include hindered phenolic stabilizers.

  These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Co., Ltd.

  Moreover, as said phosphorous acid type stabilizer, the compound as described in [0023]-[0039] of Unexamined-Japanese-Patent No. 2004-182979 can be used more preferably. Specific examples of the phosphite ester stabilizer include JP-A-51-70316, JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, Examples thereof include compounds described in Japanese Utility Model Laid-Open No. 55-13765. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical No. 2001-1745, issued March 15, 2001, Japan Society of Invention) are preferably used. be able to.

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferable specific examples of the phosphite ester stabilizer include the following compounds, but the phosphite ester stabilizer that can be used in the present invention is not limited thereto.

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible. Furthermore, a stabilizer having phenol and phosphite in the same molecule is also preferably used. These compounds are further described in detail in JP-A-10-273494. Examples of the compounds are included in the examples of the stabilizer, but are not limited thereto. As a typical commercial product, Sumitizer GP is available from Sumitomo Chemical Co., Ltd. These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  The stabilizers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. Preferably, the addition amount of the stabilizer is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and still more preferably 0.01 to 0% with respect to the mass of the thermoplastic resin. 0.8% by mass.

UV absorber:
The optical film of the present invention may contain one type or two or more types of ultraviolet absorbers. From the viewpoint of preventing deterioration, the ultraviolet absorbent is preferably excellent in the ability to absorb ultraviolet light having a wavelength of 380 nm or less and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of transparency. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose mixed ester is small. These are disclosed in JP-A-60-235852, JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6 -148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173.
The addition amount of the ultraviolet absorber is preferably 0.01 to 2% by mass of the thermoplastic resin, and more preferably 0.01 to 1.5% by mass.

Light stabilizer:
The optical film of the present invention may contain one or more light stabilizers. Light stabilizers include hindered amine light stabilizer (HALS) compounds, more specifically, US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839. 2,405, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .

  These hindered amine light stabilizers can be used alone or in combination of two or more. Of course, these hindered amine light stabilizers may be used in combination with additives such as plasticizers, stabilizers, UV absorbers, etc., and are introduced into a part of the molecular structure of these additives. Also good. The blending amount is determined within a range not impairing the effects of the present invention, and is generally about 0.01 to 20 parts by mass, preferably 0.02 to 15 parts per 100 parts by mass of the thermoplastic resin. About mass parts, and particularly preferably about 0.05 to 10 mass parts. The light stabilizing agent may be added at any stage of preparing the melt of the thermoplastic resin composition, for example, at the end of the melt preparation process.

Plasticizer:
The optical film of the present invention may contain a plasticizer. The addition of a plasticizer is preferable from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. Further, when the optical film of the present invention is produced by a melt film-forming method, the purpose is to lower the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin to be used. It will be added for the purpose of lowering the viscosity at the same heating temperature than the added thermoplastic resin. For the optical film of the present invention, for example, a plasticizer selected from a phosphoric acid ester derivative and a carboxylic acid ester derivative is preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

Fine particles:
The optical film of the present invention may contain fine particles. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the thermoplastic resin in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, more preferably 10 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably. Here, the average primary particle size of the fine particles is determined by observing the thermoplastic resin with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass with respect to the thermoplastic resin, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0%. 4% by mass.

Optical modifier:
The optical film of the present invention may contain an optical adjusting agent. Examples of the optical adjusting agent include a retardation adjusting agent, for example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230. Can be used. By adding an optical adjusting agent, in-plane retardation (Re) and thickness direction retardation (Rth) can be controlled. A preferable addition amount is 0 to 10% by mass, more preferably 0 to 8% by mass, and further preferably 0 to 6% by mass.

Second retardation layer:
In both the embodiments of FIGS. 1 and 2, the second retardation layer is a layer containing liquid crystal compound molecules fixed in an aligned state. Re (550) of the second retardation layer is preferably 26 to 50 nm, and Rth (550) is preferably 60 to 120 nm.

Examples of the liquid crystal compound that can be used for producing the second retardation layer include both a rod-like liquid crystal compound and a disc-like liquid crystal compound.
Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. These rod-like liquid crystalline compounds are fixed by introducing a polymerizable group into the terminal structure of the rod-like liquid crystalline compound (similar to the disk-like liquid crystal described later) and utilizing this polymerization / curing reaction. As a specific example, JP-A-2006-209073 discloses an example in which a polymerizable nematic rod-like liquid crystal compound is cured with ultraviolet rays. Further, not only the above-described low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. The high molecular liquid crystalline compound is a polymer having a side chain corresponding to the above low molecular liquid crystalline compound. An optical compensation sheet using a polymer liquid crystalline compound is described in JP-A-5-53016.

  Examples of discotic liquid crystal compounds that can be used for the production of the second retardation layer include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  As a molecule of the discotic liquid crystal compound, it exhibits liquid crystallinity in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. A retardation layer formed from a composition containing a discotic liquid crystal compound does not need to exhibit liquid crystallinity when finally contained in the retardation layer. For example, if a low molecular weight discotic liquid crystalline molecule having a group that reacts with heat or light is polymerized by heating or light irradiation to increase the molecular weight, the liquid crystallinity is lost. Of course, a retardation layer containing can also be used in the present invention. Preferable examples of the discotic liquid crystal compound include compounds described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

  In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in paragraphs [0151] to “0168” in JP-A No. 2000-155216.

For the formation of the retardation layer, additives such as a plasticizer, a surfactant and a polymerizable monomer may be used in combination with the liquid crystal compound. These additives will be added for various purposes such as improving the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like.
Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer and is preferably copolymerizable with the above-described polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the liquid crystal compound.
Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] in JP-A-2001-330725.
Examples of polymers that can be used include cellulose esters. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to inhibit the alignment of the liquid crystal molecules. It is more preferable.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

The retardation layer can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerization initiator described later and optional components to the surface, preferably the surface of the alignment film.
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
Application | coating of a coating liquid can be implemented by a conventionally well-known method, and the thing of the content as described in the said oriented film is mentioned.
The thickness of the retardation layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm.

The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The alignment state is preferably fixed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  The second retardation layer is a layer formed by curing the curable liquid crystal composition after bringing it into a desired alignment state. For example, it can be produced by applying a polymerizable liquid crystal to the alignment treatment surface of the alignment film, aligning it along the alignment treatment direction (generally a rubbing axis), and fixing the alignment state. As an example, there is a retardation layer formed by fixing discotic liquid crystal molecules in a so-called hybrid alignment state. In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the layer surface increases or decreases in the depth direction of the layer and with an increase in the distance from the alignment film surface. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the angle does not change in the middle of the thickness direction. In the present specification, “hybrid orientation” includes an orientation state in which the angle does not change, or the orientation state increases or decreases as a whole. Hybrid orientation in which the angle continuously changes is preferable.

  The average direction of the major axis of the liquid crystal molecules in the retardation layer is generally determined by selecting the material of the liquid crystal or alignment film used for forming the retardation layer, or by selecting the conditions of the rubbing treatment method. Can be adjusted. Further, the major axis (disk surface) direction of the liquid crystal molecules on the surface side (air side) in the retardation layer is generally an additive used together with the liquid crystal molecules used for forming the retardation layer (for example, a plasticizer, Surfactant, polymerizable monomer, polymer, etc.) can be selected by selecting the kind. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

Optical compensation film:
As described above, the first retardation layer can be used as a support, and the second retardation layer can be formed thereon by coating to produce an optical compensation film. This optical compensation film can be used in the liquid crystal display device of the present invention.

Polarizer:
The optical compensation film can be bonded to a polarizing film to produce a polarizing plate. This polarizing plate can be used in the liquid crystal display device of the present invention. For example, the optical compensation film may be bonded as a protective film on one surface of the polarizing film. In the optical compensation film, it is preferable to bond the surface of the polymer film which is the first retardation layer and the surface of the polarizing film. As the polarizing film, for example, a polarizing film obtained by dyeing a polyvinyl alcohol film with iodine and stretching the film is used. It is preferable that a protective film is also affixed to the other surface of the polarizing film. Examples of such protective films include cellulose acylate films and cyclic polyolefin polymer films, which are conventionally used as protective films for polarizing plates. The film can be used.

Hereinafter, the present invention will be described in more detail based on examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
1. Preparation of First Polymer Film for Retardation Layer • Cyclic Olefin Copolymer “TOPAS # 6013” pellets manufactured by Polyplastics were used as the cyclic olefin copolymer. It was confirmed by the above method that “TOPAS # 6013” is positive intrinsic birefringence and is an amorphous thermoplastic resin. The glass transition point of the resin was 136 ° C.
・ Cellulose acetate propionate (CAP)
Cellulose acetate propionate (CAP) was produced according to the method described in Example 1 of JP-A-2006-348123, and pelletized according to a conventional method. The composition of the CAP used was 0.15 in acetylation, 2.60 in propionylation, 2.75 in total acyl substitution, DPn = 118 in number average degree of polymerization, showed positive intrinsic birefringence, and was amorphous. It was confirmed by the above method that it was a heat-resistant thermoplastic resin. The glass transition point of the resin was 137 ° C.

-Production of first polymer film for retardation layer The above-mentioned two kinds of pellets are melt-extruded at the molding temperature shown in Table 1 below, and two rolls driven at the diameter and peripheral speed ratio shown in Table 1 below ( A film was produced by passing between a touch roll and a chill roll. Further, transverse stretching was performed at a stretching ratio shown in the following table. The surface temperatures of the two rolls were controlled and set to the temperatures shown in the following table, respectively.
In addition, the polar angle dependence of retardation is asymmetric about the normal direction (polar angle 0 °) with respect to the incident light of at least one incident surface including the normal of the layer surface of the obtained films 1 to 5 However, the film 6 was symmetrical with respect to the polar angle dependency of the retardation around the normal direction (polar angle 0 °). In addition, the tilt angle of the principal axis of the refractive index ellipsoid of each film with respect to the normal direction of the film surface, Re (550), and Rth (550) were also measured by the above-described method. These values are shown in Table 2 below.

2. Formation of second retardation layer (production of optical compensation film)
On each film produced above, a retardation layer (D layer) composed of a discotic liquid crystal composition was formed by the following method, and optical compensation films 1 to 8 were produced.
Method for forming retardation layer (D layer) comprising discotic liquid crystal composition 204.0 parts by mass of methyl ethyl ketone, 91 parts by mass of the following discotic compound, ethylene oxide-modified trimethylolpropane triacrylate (V # 360, Osaka) 9 parts by mass of Organic Chemistry Co., Ltd., 0.5 parts by mass of cellulose acetate butyrate (CAB531-1, Eastman Chemical), 3 parts by mass of photopolymerization initiator (Irgacure 907, Ciba Geigy) A coating solution was prepared by dissolving 1 part by mass of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.).
The coating solution was applied to the alignment film by 5.52 ml / m ² using a # 3.2 wire bar. This was affixed to a metal frame and heated in a thermostatic bath at 130 ° C. for 2 minutes to orient the discotic compound.
Next, ultraviolet rays were irradiated for 4 minutes using a 120 W / cm high pressure mercury lamp at 90 ° C. to polymerize the discotic compound. Then, it stood to cool to room temperature. Thus, D layer was formed and the optical compensation film was obtained.
By changing the coating amount of the coating solution at the time of forming the D layer, or by changing the composition in the coating solution, D layers having various optical characteristics shown in the following table were formed. In any D layer formed, the discotic liquid crystal molecules were fixed in a hybrid alignment state. As shown in the table below, this is a value R [+ 40 °] measured by incident light from a direction inclined + 40 ° from the normal direction with respect to the layer surface of the D layer, and a direction inclined −40 °. It was confirmed by the fact that the value R [−40 °] measured by incidence of light was not equal.

3. Production of Polarizing Plate A polarizing plate was produced using each of the optical compensation films produced above. Specifically, it is as follows.
First, iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. Each optical compensation film described in Table 3 is bonded to one surface of this polarizing film (however, the back surface of the film which is the first retardation layer (the side where the second retardation layer is not formed) And the surface of the polarizing film were bonded to each other), and 80 μm Fujitac (Fuji Film Co., Ltd.) was bonded to the other surface. In this way, two polarizing plates PL1 to PL8 each having the optical compensation films 1 to 8 as protective films were prepared.
In addition, about any of polarizing plate PL1-PL4 and PL6-PL8, the in-plane slow axis of the film and the absorption axis of the polarizing film were made orthogonal.
On the other hand, in the polarizing plate PL5, the in-plane slow axis of the film intersects the absorption axis of the polarizing film at about 45 °.

4). 3. Production of liquid crystal display device -1 Production of TN mode liquid crystal display device As a TN mode liquid crystal cell, a liquid crystal cell having a positive dielectric constant anisotropic layer is sealed between substrates by vacuum injection, and a liquid crystal cell having a liquid crystal layer Δn · d of 400 nm is prepared. did. As the liquid crystal material, a liquid crystal having positive dielectric anisotropy, refractive index anisotropy, Δn = 0.0854 (589 nm, 20 ° C.), and Δε = + 8.5 was used. Further, the twist angle of the liquid crystal cell was 90 °, and the upper and lower substrate rubbing directions of the liquid crystal cell were made substantially parallel or substantially orthogonal to the polarizing plate absorption axis when the liquid crystal cell was bonded to the upper and lower polarizing plates later. Further, the crossing angle between the absorption axes of the upper and lower polarizing plates was approximately 90 ° crossed Nicols.
Each of the produced polarizing plates PL1 to PL4 and PL6 to PL8 is bonded to the upper and lower sides of this TN mode liquid crystal cell, with each optical compensation film in Table 3 facing the liquid crystal cell, and the liquid crystal display LCD1 -LCD4 and LCD6-PLC8 were produced, respectively. In each liquid crystal display device, the rubbing direction of the liquid crystal cell substrate and the absorption axis of the polarizing film (the polarizing film disposed closer to the cell substrate) were made parallel.
In the LCD1 to LCD4, the direction in which the retardation in the tilt direction of the first retardation layer films 1 to 4 decreases from the normal direction and the side on which the optical compensation film is disposed. The rubbing direction of the cell substrate was arranged substantially in parallel.

4). -2 Production of ECB mode liquid crystal display device As an ECB mode liquid crystal cell, a liquid crystal material having a positive dielectric constant anisotropic layer is enclosed between substrates (cell gap is 3.5 μm) by drop injection, and Δn · d of the liquid crystal layer A liquid crystal cell having a thickness of 300 nm was prepared. The liquid crystal material has a positive dielectric anisotropy, a refractive index anisotropy, Δn = 0.0854 (589 nm, 20 ° C.), and a liquid crystal of about Δε = + 8.5 (for example, MLC-9100 manufactured by Merck). did. In addition, the crossing angle of the liquid crystal cell (the crossing angle of the rubbing treatment direction applied to the inner surfaces of the upper and lower substrates) is 0 °, and the absorption axis of the polarizing plate intersects with the alignment direction (rubbing direction) of the liquid crystal cell by approximately 45 °. The crossing angle between the absorption axes of the upper and lower polarizing plates was approximately 90 ° crossed Nicol.
The produced polarizing plate PL5 was bonded to the top and bottom of this ECB mode liquid crystal cell one by one and each optical compensation film in Table 3 was bonded to the liquid crystal cell side to produce a liquid crystal display device LCD5.
In the LCD 5, the direction in which the retardation in the tilt direction of the first retardation layer film 5 is tilted from the normal direction decreases, and the rubbing of the cell substrate on the side where the optical compensation film is disposed. The directions were arranged substantially parallel to each other.

The following table shows the evaluation results of the liquid crystal cell used and the value of Δn · d, the type of the optical compensation film, and the viewing angle characteristic (contrast viewing angle characteristic) where the black and white contrast ratio exceeds 10 for LCDs 1 to 8. . Note that the contrast viewing angle characteristics were evaluated by standardizing the same viewing angles of the LCDs 1 to 7 on the basis of the viewing angle exceeding the contrast ratio 10 of the LCD 8 using the optical compensation film 8 for the comparative example.
“◎” means that the viewing angle (CR> 10) is 60 ° or more in all directions.
“○” indicates that the viewing angle (CR> 10) is 40 ° or more in all directions.
“X” means that there is less than 40 ° in the vertical and horizontal viewing angles (CR> 10).

  From the results shown in the above table, in each of the TN mode liquid crystal display devices LCD1 to LCD4 and the ECB mode liquid crystal display device LCD5 of the embodiment of the present invention, the film used as the first retardation layer satisfies the predetermined requirements. It can be understood that both the LCD 7 of the comparative example that is not made and the LCD 6 of the comparative example that does not have the second retardation layer made of the discotic liquid crystal composition are excellent in viewing angle characteristics.

It is a schematic diagram which shows the structure of an example of the liquid crystal display device of this invention. It is a schematic diagram which shows the structure of the other example of the liquid crystal display device of this invention. It is the schematic diagram used in order to demonstrate the definition of the optical characteristic of a phase difference layer.

Explanation of symbols

10, 10 'Liquid crystal display device 12 Liquid crystal layers 14, 16 Cell substrates 14a, 16a Alignment treatment directions 18 and 20 applied to the inner surface of the substrate Polarizing layers 18a and 20a Absorption axes 22, 22', 24 and 24 'of the polarizing layer 1 phase difference layer 22a, 22'a, 24a, 24'a In-plane slow axis 22b, 22'b, 24b, 24'b of 1st phase difference layer The conveyance (MD) direction of 1st phase difference layer 26, 28 Second retardation layer 26a, 28a In-plane slow axis LC of second retardation layer Liquid crystal cell F1, F1 ′, F2, F2 ′ Optical compensation film PL1, PL1 ′, Pl2, PL2 ′ Polarizing plate

Claims (11)

A pair of polarizing layers arranged with their absorption axes orthogonal to each other;
Between the pair of polarizing layers, facing each other and at least one of which has a transparent electrode, the first substrate and the second substrate, and the first substrate and the second substrate. A liquid crystal cell having a liquid crystal layer formed thereon;
A liquid crystal having a first retardation layer between at least one of the pair of polarizing layers and the liquid crystal cell; and a second retardation layer between at least one of the pair of polarizing layers and the liquid crystal cell. A display device,
The first retardation layer has an asymmetry centered on the normal direction (polar angle 0 °) with respect to the incident light of at least one incident surface including the normal of the layer surface. lifting Chi, the main axis of the refractive index ellipsoid is a film which is inclined in the thickness direction, the letter when the retardation in the tilt direction of the principal axes of the index ellipsoid of the first retardation layer is inclined from the normal direction Deshon are arranged so that the alignment treatment direction of the orientation and the substrate to be reduced are parallel, said second retardation layer, Ru layers der containing molecules of the liquid crystal compound fixed in an alignment state A TN mode liquid crystal display device. The first retardation layer has the tilt angle [theta] t of the main shaft of the refractive index ellipsoid with respect to the film surface normal direction is, 0 <according to claim 1, characterized in that it consists film satisfying the [theta] t ≦ 35 ° Liquid crystal display device. The in-plane retardation Re (550) at a wavelength of 550 nm of the first retardation layer is 0 nm <Re (550) ≦ 110 nm, and the retardation Rth (550) in the principal axis thickness direction at the same wavelength is 0 nm. <liquid crystal display device according to claim 1 or 2, characterized in that the Rth (550) ≦ 200nm. The first retardation layer is, cyclic olefin copolymers, cellulose acylate, polyesters, and the claims 1-3, characterized in that it consists of a film containing at least one selected from polycarbonates The liquid crystal display device according to any one of the above. The first retardation layer is a film produced by passing a film-like melt of a composition containing a thermoplastic resin between two rolls having different peripheral speeds. the liquid crystal display device according to any one of claims 1-4. The first retardation layer is a liquid crystal display device according to any one of claims 1 to 5, characterized in that it consists of being stretched film. The second retardation layer is any one of claim 1 to 6, characterized in that contains at least one of the discotic liquid crystal and rod-like liquid crystal fixed in a state of being hybrid orientation in the thickness direction The liquid crystal display device described. The second retardation layer, a liquid crystal display device according to any one of claims 1 to 7, characterized in that a layer formed by polymerizing a composition containing a liquid crystalline monomer. Wherein the first retardation layer, a liquid crystal display device according to any one of claims 1 to 8, characterized in that the second retardation layer is disposed. Claim 1-9, characterized in that said first plane slow axis of the retardation layer, the absorption axis of the polarizing layer located closer to the first retardation layer is parallel or orthogonal The liquid crystal display device according to any one of the above. The product of the thickness d and the birefringence [Delta] n is [Delta] n · d of the liquid crystal layer is a liquid crystal according to any one of claims 1 to 1 0, characterized by satisfying the following relationships (I) Display device:
(I) 200 nm ≦ Δn · d ≦ 500 nm.

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